Question

A carbon and aluminium wire connected in series .If the combination has resistance of 30 ohm at 0°c, what is the resistance of carbon and aluminium wire at 0°c so that the resistance of the combination does not change with temperature

Answer 1

hope this will solve your doubts

Answer 2

Let RC and RAl be resistances made of carbon and Aluminium respectively at 0ºC.

 

We are given that,    RC + RAl = 30 Ω .................(1)

 

Series combination of these rseistances at a raised temperature ΔT = RC(1+αC×ΔT) + RAl(1+αAl×ΔT).............(2)

 

Since the resistance of combination does not chnage with increase of temperature, from eqn.(1) and (2), we have

 

RC + RAl = RC(1+αC×ΔT) + RAl(1+αAl×ΔT)

 

RC(αC×ΔT) + RAl(αAl×ΔT) = 0